The invention relates to a pulse radar apparatus, provided with a transmitting and receiving unit (transmitter and receiver) for the generation and the transmission of a modulated radar transmitter pulse Y.sub.t, for the reception of the signals Y.sub.r and the correlation of a signal Y.sub.r with a replica X of the emitted radar transmitter pulse Y.sub.t to obtain an in time .delta. compressed correlation signal .sigma..sub.xy (.delta.)
The invention also relates to a pulse discriminator suitable for application in such a pulse radar apparatus.
A known embodiment of such a pulse radar apparatus relates to a pulse radar apparatus provided with a pulse compression filter for the compression in time of the received radar signal Y.sub.r so that a more accurate range determination can be obtained than would have been obtained on the basis of the uncompressed received signals Y.sub.r. A carrier wave of the emitted radar transmitter pulse Y.sub.t can be modulated in frequency, phase or amplitude, the correlation of the received radar signal can be realised by a matched filter, whose frequency response corresponds to a replica X of the radar transmitter pulse. The correlation can also be established with the aid of a replica X of the radar transmitter pulse Y.sub.t. In both cases, upon reception of the radar signal Y.sub.r, a sharply peaked signal .sigma..sub.xy (.delta.) in time .delta. is obtained, having a larger amplitude than would have been obtained without compression.
A problem with pulse radar systems is their susceptability to interference signals, whether or not caused intentionally. If a pulse radar apparatus, provided with a pulse compression filter receives an interference signal which does not contain the modulation information, a sharply peaked signal .sigma..sub.xy (.delta.) will not be obtained. Nevertheless, the received interference signal, after correlation performed with the aid of the pulse compression filter, will still have a relatively large amplitude, if the amplitude of the interference signal is large. This amplitude can even be that large that the interference signal is not classified as such.